Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $233.27   12.327%   $262.0252   $262.03   $262.05   $262.00  
  Purchase #2 $245.41   4.123%   $255.5283   $255.53   $255.55   $255.50  
  Purchase #3 $117.94   11.175%   $131.1198   $131.12   $131.10   $131.10  
  Purchase #4 $197.45   7.555%   $212.3673   $212.37   $212.35   $212.40  
  Purchase #5 $181.66   3.846%   $188.6466   $188.65   $188.65   $188.60  
  Purchase #6 $158.99   10.386%   $175.5027   $175.50   $175.50   $175.50  
  Purchase #7 $120.81   11.852%   $135.1284   $135.13   $135.15   $135.10  
  7 purchase totals = $1,255.53       $1,360.3183   $1,360.33   $1,360.35   $1,360.20